Living beings, meaning humans and animals, move according to their own will. For example the seller of particular products in a store, or the party displaying products on a fair stand, would like to draw the positive attention of as many people as possible. This task becomes easier if some proven evidence exists about how objects of the interesting kind are known to make their (conscious or subconscious) decisions about moving, stopping, and viewing in a similar situation.
In order to collect experimental data about how people behave and what catches their interest, it is common to make field observations. As an example we may consider a supermarket, where a large number of products are made available on shelves. The straightforward experimental setup is one where a human observer discreetly watches the shoppers and makes notes about how they moved along the aisles and where they stopped. The drawbacks of such a setup are related to the understandable weaknesses of a human observer: he or she cannot accurately follow the behaviour of more than one object at a time; the accuracy of following any movements depends on the awareness of the observer; it is practically impossible to measure the stops of the observed object; and the human observer may even unconsciously favour following persons that he or she finds particularly attractive of conspicuous so that the results become biased.
Some of the drawbacks listed above can be at least partially avoided by replacing the human observer with a video camera that films and stores the actual happenings that take place on the observed area, and making the human observer analyse the video footage afterwards. This allows possibilities like replaying sequences, watching some events in slow motion or fast forward, and comparing the happenings on the screen to a simultaneously displayed clock. However, some of the human drawbacks still remain. Additionally this method is time consuming and laborious and cannot, by definition, provide any information in real time.